This invention pertains to methods for forming sand molds, and specifically methods for forming sand molds utilizing a matchplate, a cope flask and a drag flask, and automatic matchplate molding machines for accomplishing the same.
Foundries use automated matchplate molding machines to produce large quantities of green sand molds which in turn create metal castings. As is well known, sand molds typically comprise two halves, including a cope situated vertically on top of a drag. The cope and drag are separated by a horizontal parting line and define an internal cavity for the receipt of molten metal material. Often, sand cores may be placed in the internal cavity between the cope and the drag to modify the shape of metal castings produced by the sand molds. The cope mold has a pouring sprue to facilitate pouring of molten metal into the internal cavity of the mold. Once molten metal is received in a sand mold, it is allowed to cool and harden. Then, the sand mold can be broken apart to release the formed metal castings.
Although manual operations exist for creating sand molds, the modern way to form sand molds is through automated matchplate molding machines. Modern automated matchplate molding machines for creating sand molds are disclosed in the following patents to William A. Hunter, U.S. Pat. Nos. 5,022,512, 4,840,218 and 4,890,664, each entitled xe2x80x9cAutomatic Matchplate Molding Systemxe2x80x9d. These patents generally disclose the concept of using a flask assembly comprised of a drag flask, a cope flask, and a matchplate therebetween to form a sand mold. Like the cope and the drag of any ordinary sand mold, the cope flask is disposed vertically above the drag flask in these matchplate molding machines. As generally disclosed in these patents, the cope flask slides down upon the matchplate and the drag flask to assemble the flask assembly. Thereafter, sand magazines vertically above and below the flask assembly engage the vertically spaced open ends of the cope flask and the drag flask. Then sand in a fluid state is pneumatically blown into the cope and drag flasks. Thereafter, the flask is drawn apart to release the cope mold and the drag mold. The cope mold is then vertically spaced above the drag mold to allow for inspection of the patterned cavities formed into the molds and sometimes to allow for placement of sand cores in the drag mold such as with automatic core setting machines as shown for example in U.S. Pat. Nos. 4,590,982, and 4,848,440 to William A. Hunter. Then, the cope mold is lowered down upon on the drag mold to complete the sand mold. Although the general technique used in these machines has met with substantial commercial success, there are drawbacks. One drawback is that the machine must blow and squeeze sand vertically upward against the force of gravity into the lower drag mold.
The present inventor is aware of an attempt to introduce and blow sand through the rectangular sidewall of the cope and drag generally parallel to the matchplate rather than through vertically spaced open ends of the cope and drag. However, this creates a much: more significant problem of xe2x80x9cshadowingxe2x80x9d. Specifically, large projections on the pattern of the matchplate block and deflect the sand which can thereby create air pockets or cavities on the downstream side of the projection. Such air pockets or cavities are very undesirable as they cause molding problems in that molten metal may fill these cavities and thereby produce a faulty and misshapen metal casting.
As such, modem automatic matchplate molding machines still typically use the matchplate molding technology generally disclosed in the prior Hunter patents noted above.
The present invention is directed towards a novel method of blowing sand into horizontally spaced open ends of the cope and drag flasks while the flask assembly is turned to a horizontal orientation (with the pattern plate extending vertically). The disclosed method utilizes a flask assembly comprised of a drag flask, a cope flask, and a matchplate. The matchplate has a pattern for forming a cavity in a sand mold and is sandwiched between the cope and drag flasks. The method comprises positioning the flask assembly with the pattern plate in a vertical orientation with the cope and drag flasks horizontally opposed on opposing sides of the pattern plate. The method also includes pneumatically conveying sand horizontally into the flask assembly in a fill direction which is perpendicular to the pattern plate to fill the cope flask and the drag flask with sand.
An embodiment of present invention is incorporated in an automated matchplate molding machine for accomplishing this method. The automated matchplate molding machine includes a pair of horizontally spaced sand magazines having blow heads adapted to fill the cope flask and the drag flask with sand. The sand magazines have a fill position wherein the flask assembly is horizontally sandwiched between the sand magazines. A vertically extending parting line is defined between the drag flask and the cope flask in the fill position, such that the flask assembly is oriented in a horizontally extending manner to facilitate blowing of sand into the mold flask horizontally through the ends of the cope flask and drag flask.
Several features and aspects of the present invention are also provided to achieve a practical and economically sensible automated matchplate molding machine. According to a preferred embodiment, the cope and drag flask made be turned between upright and tilted positions. The machine disassembles the mold flask and removes the mold in the upright position and fills the mold with sand horizontally when in the turned position. In the disclosed embodiment, a rotating turret carries two mold flasks between a mold forming station and a draw station whereat the mold flask is disassembled and a sand mold is removed. An actuator such as a hydraulic cylinder cyclically rotates the turret to switch the two mold flasks between the mold forming station and the draw station. The mold flasks may also be rotated about a horizontal axis relative to the turret to facilitate turning of the mold flasks between upright and rotated positions.